Print out prediction with WEKA in Java

问题:

I am trying to make a prediction with Weka in Java, using the Naive Bayes Classifier, with the following code:

JAVA

public class Run {
    public static void main(String[] args) throws Exception {

        ConverterUtils.DataSource source1 = new ConverterUtils.DataSource("./data/train.arff");
        Instances train = source1.getDataSet();
        // setting class attribute if the data format does not provide this information
        // For example, the XRFF format saves the class attribute information as well
        if (train.classIndex() == -1)
            train.setClassIndex(train.numAttributes() - 1);

        ConverterUtils.DataSource source2 = new ConverterUtils.DataSource("./data/test.arff");
        Instances test = source2.getDataSet();
        // setting class attribute if the data format does not provide this information
        // For example, the XRFF format saves the class attribute information as well
        if (test.classIndex() == -1)
            test.setClassIndex(train.numAttributes() - 1);

        // model

        NaiveBayes naiveBayes = new NaiveBayes();
        naiveBayes.buildClassifier(train);

        Evaluation evaluation = new Evaluation(train);
        evaluation.evaluateModel(naiveBayes, test);
    }
}

TRAIN

@relation weather

@attribute outlook {sunny, overcast, rainy}
@attribute temperature real
@attribute humidity real
@attribute windy {TRUE, FALSE}
@attribute play {yes, no}

@data
sunny,85,85,FALSE,no
sunny,80,90,TRUE,no
...

PREDICT

@relation weather

@attribute outlook {sunny, overcast, rainy}
@attribute temperature real
@attribute humidity real
@attribute windy {TRUE, FALSE}
@attribute play {yes, no}

@data
sunny,85,85,FALSE,?

In the GUI the predicted output is

=== Predictions on test split ===

inst#,    actual, predicted, error, probability distribution
     1          ?       2:no      +   0.145 *0.855

How can I get this output with Java? Which method do I need to use to get this?

回答1:

public class Run {
    public static void main(String[] args) throws Exception {

        ConverterUtils.DataSource source1 = new ConverterUtils.DataSource("./data/train.arff");
        Instances train = source1.getDataSet();
        // setting class attribute if the data format does not provide this information
        // For example, the XRFF format saves the class attribute information as well
        if (train.classIndex() == -1)
            train.setClassIndex(train.numAttributes() - 1);

        ConverterUtils.DataSource source2 = new ConverterUtils.DataSource("./data/test.arff");
        Instances test = source2.getDataSet();
        // setting class attribute if the data format does not provide this information
        // For example, the XRFF format saves the class attribute information as well
        if (test.classIndex() == -1)
            test.setClassIndex(train.numAttributes() - 1);

        // model

        NaiveBayes naiveBayes = new NaiveBayes();
        naiveBayes.buildClassifier(train);

        // this does the trick  
        double label = naiveBayes.classifyInstance(test.instance(0));
        test.instance(0).setClassValue(label);

        System.out.println(test.instance(0).stringValue(4));
    }
}